1. Field
One or more example embodiments of the following description relate to a depth image generating method and apparatus and a depth image processing method and apparatus, and more particularly, to a method for generating a depth image using light of different modulation frequencies and a method of processing the generated depth image.
2. Description of the Related Art
According to one technique, a depth image may be generated by calculating a distance to an object using a time required for light to reflect from the object and to return. Currently, a time-of-flight (ToF) camera that generates a depth image using the foregoing technique is widely used. The ToF camera calculates the distance to the object using a phase delay that occurs when frequency-modulated light is reflected.
A maximum measurable distance (“rmax”) between the object and the ToF camera is determined by a modulation frequency used for the calculating. For example, in calculating the above-referenced phase delay, a phase difference between the emitted light and reflected light in the time-of-flight is calculated to be within a period of 0 to 2π radians. rmax denotes a maximum distance measurable without ambiguity, which is called a non-ambiguous distance range. Thus an object having a distance of rmax from the ToF camera corresponds to a phase difference of 2π radians. When the phase difference is greater than 2π, such as for an object located farther away from the ToF camera than rmax, the phase difference will still be measured as falling between 0 and 2π radians. Such as phenomenon may be referred to as “phase wrapping.” Thus, the measured phase difference will be smaller than an actual phase difference thereby corresponding to some distance less than rmax. Therefore, the conventional ToF camera may incorrectly determine a depth image of an object located further than a maximum measurable distance to be within a measurable distance range.
To restore a depth value of an object located a greater distance than rmax from the depth image, a single depth image or a plurality of depth images may be used. When using a single depth image, a number of mods of a pixel having a small depth value is set to be greater by one than a number of mods of a pixel having a large depth value, at a discontinuous part of the depth image. When using a plurality of depth images, the plurality of depth images may be obtained by moving a camera.